The strongest cyclone to hit India in five years killed at least 12 people in eastern Odisha state, before swinging northeastward into Bangladesh on Saturday where five more people died although more than a million had been moved to safety.

After it made landfall early on Friday, tropical cyclone Fani had lost some of its power and was downgraded to a "Deep Depression" by the Indian Meteorological Department as the storm moved inland over Bangladesh.

"The fear of a major disaster is mostly over as (Fani) has weakened," Shamsuddin Ahmed, director of the Bangladesh Meteorological Department, said.

A storm surge still breached embankments to submerge dozens of villages on Bangladesh's low-lying coast, a disaster ministry official in Dhaka said.

In all at least five people had been killed, 63 injured, and more than the 1,000 houses had been damaged, Bangladeshi authorities said.

In India, authorities were assessing the damage left behind by Fani, which had spent days building power over the northern reaches of the Bay of Bengal before tearing into Odisha.

Indian media reported that at least 12 people had died across the state, with most deaths caused by falling trees, but a mass evacuation before the tropical cyclone made landfall averted a greater loss of life.

The seaside temple town of Puri, which lay directly in the path of Fani, suffered extensive damage as winds gusting up to 200 kph (124 mph) tore off tin roofs, snapped power lines, and uprooted trees on Friday.

"Destruction is unimaginable... Puri is devastated," Odisha's Special Relief Commissioner Bishnupada Sethi told Reuters, adding that 116 people were reported injured across the state.

Video footage taken from an Indian navy aircraft showed extensive flooding in areas around Puri, with wide swathes of land submerged in the aftermath of the storm.

Odisha Chief Minister Naveen Patnaik said the electricity infrastructure in Puri and parts of an adjoining district had been completely devastated.

“We have the challenge of having to set up the entire electrification afresh,” he told reporters.

Prime Minister Narendra Modi, who is in the midst of a general election, said in a tweet that he would visit Odisha on Monday.

Massive evacuation

As cyclone Fani approached, Odisha moved 1.2 million people to safety in 24 hours, which Patnaik described as "one of the biggest human evacuations in history."

Shelters were set up in schools and other safe buildings to accommodate the evacuees, who included scores of tourists.

More than 100,000 government officials, 45,000 volunteers and 2,000 civil society groups were mobilized, and 9,000 shelters and 7,000 kitchens pressed into service, Patnaik said.

"Instead of it being a tragedy of humongous proportions, we are in the process of restoring critical infrastructure," he said.

Neighboring West Bengal state escaped substantial damage, but authorities moved nearly 42,000 people to safer locations.

"Electricity has been restored in most places. In the next two days, the situation will be normal," West Bengal chief minister Mamata Banerjee said in a statement.

About 1.2 million people living in the most vulnerable districts in Bangladesh had also been moved to some 4,000 shelters.

Some major cyclones in India

In 2017, cyclone Ockhi killed 365 people and displaced hundreds, according to India's home affairs ministry. In October last year, officials in Odisha evacuated hundreds of thousands of people when another cyclone struck.

In 2013, cyclone Phailin, the second-strongest tropical system following the 1999 Odisha cyclone, battered India, leaving 30 people died. Massive evacuation kept the toll down.

The 1999 Odisha cyclone, also known as Paradip cyclone, was the strongest and deadliest tropical cyclone ever recorded in the North Indian Ocean since the 1991 Bangladesh cyclone, and deadliest Indian storm since 1971, killing about 10,000 people and causing extreme damage in its path of destruction.